Method for Producing a Tubular Semifinished Product From Fluorine-Doped Quartz Glass

A method for producing a tubular semifinished product of fluorine-doped quartz glass, the method comprising the following steps:

• (a) providing a substrate tube consisting of fluorine-doped quartz glass;
• (b) forming, in a deposition process, SiO2 particles by means of plasma burners in the presence of fluorine, and depositing said particles in layers on a cylindrical outer surface of the substrate tube rotating about longitudinal axis thereof so as to form a mother tube of fluorine-doped quartz glass;
• and
• (c) elongating the mother tube in an elongation process so as to obtain the tubular semifinished product,
• wherein method step (a) comprises an iterative method that comprises the following steps:
• (A) in a starter tube deposition process, forming SiO2 particles are formed by means of plasma burners in the presence of fluorine, and depositing said particles so as to form a starter tube on a cylindrical outer surface of a support body rotating about a longitudinal axis thereof, and
• (B) in a starter tube elongation process, elongating the starter tube into a tube of fluorine-doped quartz glass, wherein said tube is the support body in a subsequent iteration of step (A) or as the substrate tube provided by method step (a).